1. Technical Field
This invention relates to the identification of the locations of faults in a telecommunications network. In particular it concerns networks connecting computing devices to the internet.
2. Related Art
A computing device can be connected to the Internet using a broadband router which links into a telephone line connected to a network exchange. Faults can occur anywhere in this sequence, either between the computing device and router, on the line between the router and the network exchange (including any intermediate connections), or in the computing device, or in the router, or in the exchange itself.
In a network with redundant duplicate connections, failure of an individual link may result in an impairment of service, rather than total loss of service, as the customer terminals may be able to connect by some other route. One example of such redundancy by duplication is the use of a terminal with a wireless connection capability. In the event that a connection by way of the closest or preferred wireless access point fails, such a terminal may have the capability to connect to a different wireless access point, or it may be able to form ad-hoc connections with other similar terminals which can, in turn access the network. It is also known to create an ad-hoc system between two different access points and to re-direct communication between a first access point and the infrastructure via the second access point.
Telecommunications network operators can check for faults using monitoring systems operating from a central location in the network, looking outwards towards the end users. However, it is not feasible to routinely check all network connections very frequently. Moreover, the absence of a response from an end-user may be from a cause other than a fault—the user may simply have switched his terminal off—so such checks cannot be reliable indicators of faults. Consequently, when a customer's connection to the Internet fails, the network operator is usually not immediately aware of this failure. In general, the network operator is only alerted to a fault when the end-user reports it.
Reliance on alerts being raised by the customers causes a delay in detection: in particular, a fault will not be identified until it has already caused inconvenience to the customer. In a network with good duplicate connections, the failure of a link may merely result in an impairment of that service as a result of the reduced capacity available on the remaining connections, rather than the complete loss of the service to some users. Consequently, the failure of an individual link may actually go un-noticed, or at least unreported, until a period of high demand—or the occurrence of a second failure—overloads the system. A failure in such a situation would result in greater inconvenience than would be the case had the initial problem received more prompt attention.
A problem with a centralized approach to fault management is that it is often difficult to identify the location of a fault. This is a particular problem in situations where customer use is infrequent: inability of the network management system to detect activity on a particular connection does not necessarily imply that the connection has failed. The response a line gives to a test signal will depend on what equipment, if any, is connected to the far end at the time the test signal is sent.